The study of the enzymes that synthesize and degrade lecithin in the human newborn lung, and their control. Purification and characterization of these enzymes with assays at maximal conditions will be sought through salt gradient precipitation, solvent extraction, and chromatographic techniques. Enzyme activities of autopsy specimens will be studied in relationship to such factors as gestational age, type of pulmonary disease (respiratory distress syndrome, bronchopulmonary dysplasia) and familial respiratory distress. The control of lecithin synthesis and turnover will be investigated by studying relative enzyme activities at maximum conditions to determine kinetic constants, and at similar conditions with existing endogenous substrate levels. The role of other substances, such as lysolecithin, on control of enzyme activity will also be studied.